How can I find a possible electrical short that affects more than one system?

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I turned the key to start but got nothing. The key was stuck in the on position and could not shift. Waited 15 minutes and system corrected itself and was able to start truck. However, when I put my foot on the brake the rear camera went on. Then the turn signals blinked fast like a light bulb was out. Also, left side a/c blew cold and right side blew hot. Next day everything was normal. After about 15 minutes drive the rear camera went on when I braked and the turn signals blinked fast as if the hazard lights were on. This condition is intermittent. Next time I start everything might work. Go figure. Finally, this hasn't happened for a while, the right side a/c actuator doors will open and close.